Depending on the amount of load to be added/removed (variations)?
If the variations are low: one in ISO and other machines in droop are preferable, since the ISO machine can handle variations in load without getting overloaded or motored.
If the variations are high: All machines in droop are...
I have a sub main distribution board which feeds the final distribution boards and 10's of individual loads. Now considering that I have an option of applying both MCBs and MCCBs as the outgoing circuit breakers.
MCBs - Standard ratings are available from 0.5A to 80A.
MCCBs - Standard ratings...
My specification calls for a short circuit rating of 35kA rms and 77kA peak value for a junction box with a bus bar in it.
The vendor proposes a junction box with a short circuit tested at 90kA for 0.1s.
He justifies that peak mechanical effects (potential damage) to a product due to a short...
Because fault currents are very less as the faults get closer to neutral, this can be detected by REF whereas Differential may not detect this. As most of the times, the faults of those lesser magnitude comes under the slope setting.
The Saudi Aramco specification says,
8.3.1 IEC or Ex labeled equipment/component meeting requirement of IEC 60079 and certified by one of the agencies in the approved IECEx certification bodies (ExCBs) under IECEx Certified Equipment Scheme is acceptable. Method of protection must be marked...
The attached article says that the relay setting should be above the sum of the exciting currents in the parallel CTs. ( I got this article from one of the old threads on this same forum).
Does it mean the exciting currents of the CTs circulates through the relay path?
how does the exciting...
If understand that "P2" (Primary) of the CTs to be positioned towards the protected object; My question is concerned with the other core in the CT supplying to Metering in the secondary of the power transformer - green highlighted in the below image, Is there a possibility to wrong polarity...
Yes, it is not connected to the Diff/REF relay in the above picture. That is why I asked you to consider. These pictures are not related to my project.
If these CTs are connected to the Diff/REF relays, is the position/polarity of the CTs are correct. As I studied, these position of CTs are...
Dear Mr che,
My question is related to the position of the primary of CTs for differential and REF protections.
Generally P1 of the CT is connected to the source side and P2 is connected to the load side.
In the above image, consider the top portion as primary of the power transformer (source...
Is the attached arrangement of CTs correct for differential protection of transformer? The "P2" of CTs on both the primary & secondary of transformer are towards the transformer.
https://files.engineering.com/getfile.aspx?folder=f1a521f2-e0c4-4b5f-8b42-8004cea93d6e&file=rkXxQ.png
Thanks RRaghunath,
Can I understand that for external faults, if one of the phase CT gets saturated, the secondary currents of the unfaulted phase CTs and the secondary current from the neutral CT would circulate through the faulted CT secondary.
Is the High impedance REF relay current...
The stabilizing resistor in high Impedance REF assists in such a way that the derived current in the relay circuit (Rst + Rp) cannot reach the relay setting threshold when the maximum through current saturates a CT with its DC component.
Generally, the faults closer to neutral have less...
